The present invention relates generally to apparatus for stabilizing the flow of a fluid and more particularly to apparatus which provides an adjustable quantity of tubules disposed in a fluid flow path to assure laminar flow of the fluid therethrough.
In a fluid which is flowing axially through an enclosed fluid flow path, the mass flow rate is proportional to pressure drop if the flow is laminar. However, if the flow is turbulent this proportional relationship does not hold. Operations such as fluid mass flow rate measurement and control cannot conveniently be accomplished unless the proportional relationship between the flow rate and the pressure drop is maintained, and therefore it is necessary to assure laminar flow conditions in order to carry out such operations.
Assuming a given viscosity and velocity, laminar flow of a fluid can be achieved by providing a fluid flow path characterized by a high ratio of length to effective hydraulic radius ("EHR"), where EHR is the cross-sectional area of the flow path divided by the perimeter thereof. If the length-to-EHR ratio of a given flow path is not high enough to assure laminar flow, said ratio can be increased by placing a flow restrictor characterized by a high length-to-EHR ratio across the path such that the fluid is constrained to flow through the restrictor. Various flow restrictors characterized by high length-to-EHR ratios have been proposed, and devices exemplary of such flow restrictors are disclosed in U.S. Pat. No. 4,497,202 issued to Mermelstein and in other references discussed therein.
Many flow restrictors are fabricated of metal or the like and are subject to attack by corrosive fluids. Some such fluids attack one kind of metal and some attack another. Accordingly, if a device which requires a flow restrictor is to be usable with more than one corrosive fluid, several flow restrictors made of different materials may have to be provided, one such restrictor being installed at any given time according to the particular fluid then in use.
In addition, a given flow restrictor functions optimally over a limited range of fluid flow parameters such as temperature, density, viscosity, flow rate and pressure. Hence several flow restrictors, each optimized for different values of these parameters, must be kept on hand and installed as needed.
From the foregoing, it will be apparent that there is a need for a fluid flow stabilizer which can achieve laminar flow of a fluid in an enclosed flow path, which is not adversely affected by corrosive fluids, and which is readily adjustable for optimum performance over various ranges of fluid flow parameters.